Abstract:

Rare species not only contribute to a community’s species abundance distribution pattern, but are also important contributors to alpha diversity. In this study, we studied the changes of species diversity and species abundance distribution pattern in the subalpine meadow of Gannan at different slope directions. To do this, we used means of additive allocation and RAD package of Fortran software fitting to analyze species abundance distribution pattern and α diversity to determine the contribution of rare species in species abundance distribution pattern. The results show that: (1) From southern to northern slopes, environmental factors changed greatly as the total soil phosphorus, soil organic carbon, available phosphorus, carbon-nitrogen ratio and water content increased. The ratio of nitrogen to phosphorus and soil pH showed decreasing trends. Soil total nitrogen was significantly lower in the west slope than in other slope directions, while available nitrogen has no significant difference in all aspects. (2) The influence of rare species on the community’s species diversity increased from south to north. However, compared with the scenarios of removing rare species and the condition of removing non-rare species, the effect of removing rare species in all aspects was higher than that of removing non-rare species. Therefore, the relative contribution of rare species to species diversity was higher than that of non-rare species. (3) The resource acquisition strategy of rare species was found to be random (the random fraction). However, the niche preemption model (the geometric series) is the main model for non-rare species. Due to the large dispersal capacity of rare species, the niche overlap among species will be more obvious in the communities with high species diversity. In this way, the increase of species diversity is inhibited, thus maintaining the biodiversity.

Key words: Qinghai-Tibet Plateau, species diversity, species abundance distribution pattern, rare species, resource allocation